It is well known that DC to DC converters can be made to step down, that is BUCK, or step up, that is BOOST, a DC input voltage to a DC output voltage. The DC to DC converter may comprise an inductor in association with two or more transistors such that the current in the inductor can be built up such that energy is stored in it by virtue of its magnetic field, and then that energy can be discharged from the inductor in order to charge a storage capacitor at the output of the DC to DC converter. Each time the transistors are switched some energy is lost, either through ohmic heating of the transistor as it transitions from a low impedance state to a high impedance state, or to currents lost to the control electrode, such as the base of a bipolar transistor or the gate of a field effect transistor as the transistor is switched on and off. These losses are insignificant when the load served by the DC to DC converter is drawing significant portions of an amp. However, where the load draws very little current, for example because it is a mobile telephone receiver designed with a long battery life in mind, then the losses due to switching the transistors on and off become more significant.
It should be noted that such inductor based DC to DC converters inherently require a ripple current to occur in the inductor otherwise the converter loses its ability to regulate its output voltage in response to changes of load current.